A diagrammatic representation has been given of said fitting, according to the known prior art, in FIG. 1 of the drawings. A furnace (1) of any shape accommodates internally, in a large part of the volume thereof, a liquid fluid at high temperature, defined by an aluminium alloy or the like, while leaving free an internal volume (V1) of air. A vertical plunger device (2) is placed in the upper part of the furnace with, in outward projection, the mould (3) accommodating the part for production (4). The tube leads into the lower part of the mould, which is provided with a site accommodating a filter (5). A mould accommodating the part for production is placed above the furnace. The mould is coupled to the furnace via a plunger tube. Between the plunger tube and the mould is placed a filter so that the oxides can be removed. A pressure exerted on V1 brings the fluid up through the tube passing through the filter and then filling the cavity of the mould. These filters are made in practice in the form of a flat plate that may be, for example, in the shape of a disk, a square, a rectangle, or in a lattice pattern with a more or less significant mesh. The function of these filters, whether made of metal or fibre glass, is therefore to restrict and reduce, or even prevent, the transfer of aluminium oxides and the like from the bath into the mould for the production of the part to be obtained. These filters must be held in position in their accommodation seat at the feeder head of the part in order to provide an effective seal. The configuration of a prior art filter has been shown in FIG. 2.
Various problems are encountered however in practice, namely:                A problem of filter stability is encountered since they tend to come away from their seat under the effect of the pressures exerted by the movement of the fluids thereby causing losses of leak tightness and therefore a lack of control over the filtration of the oxidised particles. The movement of the fluid brings about turbulence that cause the filters to lift and the leak tightness to be eliminated or the filter to distort into a V-shape, that lets the unfiltered liquid alloy through. This situation has been shown diagrammatically in FIGS. 3 and 4. The reference AM shows the inflow of the metal through the tube, the reference PIM the lower part of the mould, the reference PSM, the upper part of the mould, and the reference DI the diffuser. The distortion of the filter has also been shown.        Another problem lies in the fact that when liquid metal is run onto prior art filters, they degas thereby releasing gas in the mould that may create oxides.        Furthermore, the filters are, to the knowledge of the applicant, installed in the mould bottom manually.        
Another problem lies in the fact that the filters produced in accordance with the prior art are not recoverable. Prior art filters are too dense and they fall to the bottom of the liquid metal baths which makes it impossible to recycle the feeder head/filter unit.
The approach adopted by the applicant has therefore been to give consideration to a new design for filters that are able to provide an answer to the various problems raised. This consideration has revolved, on the one hand, around the filter structure itself and, on the other hand, around the configuration thereof.
The solution offered by the invention provides an answer to the various problems.